Phase-field Model of Electromechanical and Optical Properties of Ferroelectric Domain Structures

铁电畴结构机电和光学特性的相场模型

• 批准号: 2133373
• 负责人: Long-Qing Chen
• 金额: $ 50.55万
• 依托单位: Pennsylvania State Univ University Park
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-08-01 至 2026-07-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2133373&HistoricalAwards=false
• 关键词: Phase; field; Model; Electromechanical; Optical

NONTECHNICAL SUMMARYThis award supports theoretical and computational research, and education to develop computational models and tools for studying piezoelectricity and light transparency of ferroelectric crystals. The piezoelectricity of a material characterizes the ability of the material to generate an electric voltage difference when it is subject to a mechanical stress or to generate a mechanical motion when the materials is subjected to an electric voltage difference or electric field. Light transparency of a solid measures the fraction of the incident visible light transmitted through the material, and it is limited by the amount of light reflection and scattering on the outside surfaces as well as the internal interfaces and the light adsorption inside the solid. Ferroelectrics are materials that contain high density of electric dipoles or polarization in the absence of an applied electric field, and they are the major class of piezoelectric materials exhibiting high piezoelectricity. However, the ferroelectric crystals that possess the highest piezoelectricity tend to be those containing many spatial regions of uniform electric polarization with different polarization directions separated by so-called ferroelectric domain walls. Most of these domain walls scatter and reflect light, and thus even single crystal ferroelectric materials are not completely transparent or tend to be opaque at best. The PI will develop computational models and tools to study both piezoelectricity and light transparency of ferroelectric crystals. The models and tools will be employed to find the optimal combination of optical transparency and piezoelectricity through understanding the roles of the ferroelectric domain wall orientations and domain wall density. Transparent ferroelectric crystals with high piezoelectricity have potential applications in high-throughput photoacoustic biomedical imaging, transparent actuators, self-energy-harvesting touch screens, and invisible robotic devices. The project will train graduate students to become experts in the areas of computational materials science, physics of piezoelectricity, and light propagation in inhomogeneous solids. Graduate students will also be trained in mentoring by co-supervising the research of undergraduate students in materials science and engineering or physics in the PI’s group.TECHNICAL SUMMARYThis award supports theoretical and computational research, and education with the main goal to fundamentally understand the science underlying the roles of domain structures in both piezoelectricity and light transparency of ferroelectric crystals. The award will support the development of a phase-field model of ferroelectric domains and piezoelectricity in both multidomain single crystals and polycrystalline ceramics in the presence of electronic and ionic defects and a spectral method in space with frequency-domain description in time for solving the Maxwell equations of light propagation and obtaining the light transmission spectrum for arbitrary ferroelectric domain structures. The PI and his graduate students will use the computational tools to study the evolution of domain walls, piezoelectricity, electronic charge carriers, and the light transparency at different frequencies under different ferroelectric polarization poling protocols. The developed computational framework and advance in fundamental understanding will then be harnessed to guide the design of ferroelectric domain structures to achieve desired electromechanical and optical properties, and to search for ferroelectric crystals possessing both high piezoelectricity and light transparency. The PI’s group has hosted numerous undergraduate students in the past for research training in computational materials research, including two recent NSF-REU students subsequently awarded NSF graduate fellowships. During the proposed project period, the PI’s group will continue to actively recruit both undergraduate students from its home institution and those from other institutions through the Penn State NSF-REU program(s) for research training as well as for mentoring training for the graduate students involved in the project.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

该奖项支持理论和计算研究，以及开发用于研究铁电晶体的压电性和透光性的计算模型和工具的教育。材料的压电性表征材料在经受机械应力时产生电压差或在材料经受电压差或电场时产生机械运动的能力。固体的透光率测量入射可见光透射通过材料的分数，并且它受到外表面上的光反射和散射的量以及内部界面和固体内部的光吸收的限制。铁电体是在没有施加电场的情况下包含高密度电偶极子或极化的材料，并且它们是表现出高压电性的主要类别的压电材料。然而，具有最高压电性的铁电晶体倾向于包含具有由所谓的铁电畴壁分隔的不同极化方向的均匀电极化的许多空间区域的那些。这些畴壁中的大多数散射和反射光，因此即使单晶铁电材料也不是完全透明的，或者最多是不透明的。PI将开发计算模型和工具来研究铁电晶体的压电性和透光性。通过理解铁电畴壁取向和畴壁密度的作用，这些模型和工具将被用来找到光学透明性和压电性的最佳组合。具有高压电性的透明铁电晶体在高通量光声生物医学成像、透明致动器、自能量采集触摸屏和隐形机器人设备中具有潜在的应用。该项目将培养研究生成为计算材料科学，压电物理学和非均匀固体中的光传播领域的专家。研究生也将通过共同指导PI小组中材料科学与工程或物理学的本科生的研究来进行指导培训。技术总结该奖项支持理论和计算研究以及教育，主要目标是从根本上理解铁电晶体的压电性和透光性中畴结构作用的科学基础。该奖项将支持在存在电子和离子缺陷的情况下开发多畴单晶和多晶陶瓷中的铁电畴和压电性的相场模型，以及在时间上具有频域描述的空间光谱方法，用于求解光传播的麦克斯韦方程并获得任意铁电畴结构的光透射光谱。PI和他的研究生将使用计算工具来研究畴壁，压电性，电子电荷载流子的演变，以及在不同铁电极化极化协议下不同频率下的光透明度。开发的计算框架和进步的基本理解，然后将利用指导设计的铁电畴结构，以实现所需的机电和光学性能，并寻找具有高压电性和透光性的铁电晶体。PI的小组在过去曾接待过许多本科生进行计算材料研究的研究培训，包括最近的两名NSF-REU学生，随后获得了NSF研究生奖学金。在拟议项目期间，PI小组将继续通过宾夕法尼亚州立大学NSF-REU项目积极从其所在院校和其他院校招收本科生该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的知识产权进行评估来支持。优点和更广泛的影响审查标准。

项目成果

Phase-field simulation of domain size effect on dielectric and piezoelectric responses in K0.5Na0.5NbO3 epitaxial thin films with superdomain structures

• DOI: 10.1016/j.actamat.2023.118777
• 发表时间: 2023-02
• 期刊: Acta Materialia
• 影响因子: 9.4
• 作者: Menghan Zhou;Bo Wang;Kun Peng;Han Liu;Long-Qing Chen;C. Nan